1. Field of the Invention
The present invention relates to a dynamic damper mounted on a drive shaft for an vehicle, and more particularly, to a dynamic damper characterized by varying thicknesses for each portion of a bridge portion formed between a main body portion into which a mass body is inserted and a connecting portion into which a drive shaft is inserted.
2. Description of the Related Art
Generally, a drive shaft is installed between a transmission and wheels of a vehicle and transmits driving power from an engine to the drive shaft through the transmission, thereby driving the wheels. In particular, vibration and noise are generated when unstable steering occurs due to a frictional force and a difference in the number of rotations between the left and right wheels during a process of transmitting driving power from the engine to the wheels of the vehicle. Therefore, as illustrated in FIG. 1, when a differential driving device adjusts the number of rotations of the left and right wheels to provide steering stability, a constant velocity joint 2 is disposed between the drive shaft and the transmission, and a dynamic damper 3 is mounted on a drive shaft 1 to attenuate vibration and noise.
The dynamic damper is mounted directly on or inserted into the drive shaft, and generates a predetermined resonant frequency to absorb or eliminate (e.g., reduce) vibrational energy transmitted to the drive shaft, thereby performing a function of attenuating vibration and noise. Typically, the dynamic damper includes a cylindrical rubber damper coupled directly to an exterior circumferential surface of the drive shaft, and a mass damper which is inserted into the rubber damper and has a steel ring shape. The rubber damper transmits vibration generated from the drive shaft to the mass damper, and the mass damper receives vibration and vibrates while absorbing natural vibration of the drive shaft, thereby reducing vibration and noise of the drive shaft. However, the dynamic damper in the related art does not prevent the occurrence of anti-resonance due to a low damping value.
Therefore, to prevent the anti-resonance, a dual mode dynamic damper has been used in which as illustrated in a side view of the damper in FIG. 2A. For example, a cross-sectional view of FIG. 2B taken along line A-A′, spline parts 4 illustrates a protruding wedge shape formed on a bridge portion between fixing portions between the mass damper of the dynamic damper 3 and the drive shaft when viewing a longitudinal section of the damper 3. Further, as illustrated in a cross-sectional view of FIG. 2C taken along line B-B′, the spline part is not formed (for convenience, referred to as a ‘non-spline part 5’) when viewing a cross section of the damper 3, for example, two resonant frequencies are generated by both of the spline part 4 and the non-spline part 5, thereby eliminating anti-resonance. However, the dual mode dynamic damper attenuates the anti-resonance, but has a limitation in attenuating vibration applied to the drive shaft because of a temperature variation by which a resonant frequency of the dynamic damper varies based on the seasons.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to those of ordinary skilled in the art.